The present invention broadly relates to a new and improved rotating or rotary isolating switch, especially an encapsulated or enclosed rotating or rotary isolating switch. '
Generally speaking, the rotating or rotary isolating switch comprises at least two fixed contacts per switched phase, each such fixed contact consisting of one upper fixed or stationary contact and one lower fixed or stationary contact, and a rotary or movable contact rotatable about an axis of rotation. This rotary or movable contact is in constant engagement with the lower fixed or stationary contact and, by its rotation about the axis of rotation, can be brought into and out of engagement with the upper fixed or stationary contact. The rotary or movable contact is supported on a support made of electrically insulating material. The support is rotatable about the above mentioned axis of rotation and each rotary or movable contact projects radially from this support.
Such a rotating or rotary isolating switch in enclosed or encapsulated and three-pole execution is known from the German Patent Publication No. 2,924,630, published Jan. 29, 1981. In this rotating or rotary isolating switch three movable contacts, each constructed in the form of a knife, are anchored against relative rotation on a straight or linear hexagonal shaft made of insulating material. The contour of each of these movable contacts possesses two extensions or bulges which extend radially outwards. The first extension or bulge is normally always in engagement with a fixed contact. This fixed contact possesses two contact surfaces which lie opposite each other and which are in the form of a circular ring segment. The above mentioned first extension or bulge of the movable contact engages in a frictional manner between these two contact surfaces. Analogously, the second extension of the movable contact engages between facing contact surfaces of a second fixed contact in a frictional manner. These contact surfaces of the second fixed contact do not, however, possess the form of a circular ring segment in order that the second extension of the movable contact may also be brought out of contact with or disengaged from the second fixed contact so as to bring about a separation or mutual isolation of the two fixed contacts.
During a switching movement both extensions of the movable contacts therefore have to carry out a frictional or surface wiping movement in relation to the contact surfaces of the fixed contacts. Since all these contact surfaces are arranged radially remote from a common axis of rotation determined by the hexagonal shaft, the hexagonal shaft has to exert a considerable turning moment or torque on the movable contacts and an appropriate drive means for driving or turning the hexagonal shaft has to apply this turning moment or torque. Furthermore, each movable contact of this known rotating or rotary isolating switch is anchored by means of two half shells which conjointly surround the hexagonal shaft and which are biased or preloaded together. One of the half shells is fastened directly to the movable contact, for instance by welding. The half shells only engage with the outside surface of the hexagonal shaft. Therefore the risk exists that with time play will develop in the direction of rotation between the hexagonal shaft, which is made of insulating material, and the respective movable contacts which are anchored thereto.